[PATCH v2 1/1] NFS: Convert from readpages() to readahead()

[Dave Wysochanski <dwysocha@redhat.com>]

Convert to the new VM readahead() API which is the preferred API
to read multiple pages, and rename the NFSIOS_* counters and the
tracepoint as needed.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
---
 fs/nfs/file.c              |  2 +-
 fs/nfs/read.c              | 18 +++++++++++++-----
 include/linux/nfs_fs.h     |  3 +--
 include/linux/nfs_iostat.h |  6 +++---
 4 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 209dac208477..cc76d17fa97f 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -519,7 +519,7 @@ static void nfs_swap_deactivate(struct file *file)
 
 const struct address_space_operations nfs_file_aops = {
 	.readpage = nfs_readpage,
-	.readpages = nfs_readpages,
+	.readahead = nfs_readahead,
 	.set_page_dirty = __set_page_dirty_nobuffers,
 	.writepage = nfs_writepage,
 	.writepages = nfs_writepages,
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index d06b91a101d2..296ea9a9b6ce 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -397,15 +397,19 @@ int nfs_readpage(struct file *file, struct page *page)
 	return ret;
 }
 
-int nfs_readpages(struct file *file, struct address_space *mapping,
-		struct list_head *pages, unsigned nr_pages)
+void nfs_readahead(struct readahead_control *ractl)
 {
+	struct file *file = ractl->file;
+	struct address_space *mapping = ractl->mapping;
+	struct page *page;
+	unsigned int nr_pages = readahead_count(ractl);
+
 	struct nfs_readdesc desc;
 	struct inode *inode = mapping->host;
 	int ret;
 
 	trace_nfs_aop_readahead(inode, nr_pages);
-	nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
+	nfs_inc_stats(inode, NFSIOS_VFSREADAHEAD);
 
 	ret = -ESTALE;
 	if (NFS_STALE(inode))
@@ -422,14 +426,18 @@ int nfs_readpages(struct file *file, struct address_space *mapping,
 	nfs_pageio_init_read(&desc.pgio, inode, false,
 			     &nfs_async_read_completion_ops);
 
-	ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
+	ret = 0;
+	while (!ret && (page = readahead_page(ractl))) {
+		prefetchw(&page->flags);
+		ret = readpage_async_filler(&desc, page);
+		put_page(page);
+	}
 
 	nfs_pageio_complete_read(&desc.pgio);
 
 	put_nfs_open_context(desc.ctx);
 out:
 	trace_nfs_aop_readahead_done(inode, nr_pages, ret);
-	return ret;
 }
 
 int __init nfs_init_readpagecache(void)
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 140187b57db8..a5aef2cbe4ee 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -586,8 +586,7 @@ extern int nfs_access_get_cached(struct inode *inode, const struct cred *cred, s
  * linux/fs/nfs/read.c
  */
 extern int  nfs_readpage(struct file *, struct page *);
-extern int  nfs_readpages(struct file *, struct address_space *,
-		struct list_head *, unsigned);
+extern void nfs_readahead(struct readahead_control *);
 
 /*
  * inline functions
diff --git a/include/linux/nfs_iostat.h b/include/linux/nfs_iostat.h
index 027874c36c88..418145f23700 100644
--- a/include/linux/nfs_iostat.h
+++ b/include/linux/nfs_iostat.h
@@ -22,7 +22,7 @@
 #ifndef _LINUX_NFS_IOSTAT
 #define _LINUX_NFS_IOSTAT
 
-#define NFS_IOSTAT_VERS		"1.1"
+#define NFS_IOSTAT_VERS		"1.2"
 
 /*
  * NFS byte counters
@@ -53,7 +53,7 @@
  * NFS page counters
  *
  * These count the number of pages read or written via nfs_readpage(),
- * nfs_readpages(), or their write equivalents.
+ * nfs_readahead(), or their write equivalents.
  *
  * NB: When adding new byte counters, please include the measured
  * units in the name of each byte counter to help users of this
@@ -98,7 +98,7 @@ enum nfs_stat_eventcounters {
 	NFSIOS_VFSACCESS,
 	NFSIOS_VFSUPDATEPAGE,
 	NFSIOS_VFSREADPAGE,
-	NFSIOS_VFSREADPAGES,
+	NFSIOS_VFSREADAHEAD,
 	NFSIOS_VFSWRITEPAGE,
 	NFSIOS_VFSWRITEPAGES,
 	NFSIOS_VFSGETDENTS,
-- 
1.8.3.1